Propiolic acid, esters

Rh complexes are examples of the most effective catalysts for the polymerization of monosubstituted acetylenes, whose mechanism is proposed as insertion type. Since Rh catalysts and their active species for polymerization have tolerance toward polar functional groups, they can widely be applied to the polymerization of both non-polar and polar monomers such as phenylacetylenes, propiolic acid esters, A-propargyl amides, and other acetylenic compounds involving amino, hydroxy, azo, radical groups (see Table 3). It should be noted that, in the case of phenylacetylene as monomer, Rh catalysts generally achieve quantitative yield of the polymer and almost perfect stereoregularity of the polymer main chain (m-transoidal). Some of Rh catalysts can achieve living polymerization of certain acetylenic monomers. The only one defect of Rh catalysts is that they are usually inapplicable to the polymerization of disubstituted acetylenes. Only one exception has been reported which is described below. 

The reaction between secondary enediamines and propiolic acid esters has been studied in detaiP. In aprotic solvents such as benzene and dioxane, 8 adds to methyl propiolate at ambient temperature to give almost quantitatively product 118 with a tron -configuration of the new double bond, as indicated by a Jhh coupling constant of around 16 Hz in the NMR spectrum. It appears that the reaction proceeds via an ene-addition mechanism. In refluxing ethanol, the C-adducts 118 are converted to the heterocyclic compounds 119. The direct transformation of 8 to 119 is easily achieved in alcoholic solvents. 1,1-Enediamines with jS-nitro, ester and acetyl substituents undergo analogous addition and cyclocondensation reactions to give heterocyclic compounds jj5(39,i2o A -Ethynylcarbonyl imidazole behaves similarly to propiolic acid esters ° (equation 41). 

Thiols add to propiolic acid esters under the influence of acid or base catalysts [150], The ratio of Z E isomers produced depends on both the solvent and the nature of the catalyst used. When neutral alumina is employed as catalyst the reaction gives high yields of the olefinic product and high Z.E ratios (e.g. equation 4,39) in comparison to the results with homogeneous, basic catalysts [151]. 

PdCl2 Propargyl alcohol, propiolic acid, propiolic acid ester ( 90%) 132,133... 

PPh3)2PdCl2 Propiolic acid ester ( 80%), propargyl alcohol 133... 

Well-defined Ru carbene catalysts, which are well known as very active catalysts for olefin metathesis reactions, have been elucidated to polymerize un- and substituted acetylenes such as a,co-diynes, propiolic acid esters, and DPAs. Grubbs 1st, 2nd-, and 3rd- (23-25, respectively. Figure 8) generation catalysts... 

For the synthesis of functionalized acrylates, a palladium-catalyzed reaction combining two unsaturated fragment is well known for propiolic acid esters (see also... 

Equimolar quantities of acetylenedicarboxylic acid esters (166) and 2-N-substituted l,3-dithiolan-2-imines (169) undergo a 1,3-dipolar cycloaddition, with elimination of ethylene, to yield A -thiazoline-2-thiones (168). The same products result from 2-alkylthio-l,3,4-thiadiazoline-5-thiones (167), with loss of alkyl thiocyanate as shown. They are desulphurized to the corresponding thiazolinones (172) by the action of mercuric acetate in acetone-acetic acid. They react with two further moles of the acetylenic reagent (166) to produce the spiranes (170 e.g. = R = COzMe), which are in turn desulphurized and cleaved by Raney nickel to the AMhiazoline derivatives (171). An analogous series of reactions was carried out using propiolic acid esters. ... 

The reaction of propiolic acid or its esters with 2-aminothiazole yields 7H-thiazolo[3.2o]pyTimidine 7-one (109) (Scheme 74) (273), The reaction probably proceeds by initial nucleophilic attack of 2-aminothiazole on the sp C followed by intramolecular addition of ring nitrogen to spC. 

The reaction of bromine with (pyrazol-4-yl)acrylic acid and its esters and the subsequent dehydrobromination of the products have been investigated by Finar and Okoh [73JCS(P1)2008]. Attempts to dehydrobrominate bromoacrylic acids (20) to 3-( 1 -phenylpyrazol-4-yl)propiolic acids 22 failed, but were successful when bromoesters 21 were used (Scheme 32). 

After acetylenedicarboxylates, esters of propiolic acid are the second common group of reagents for 1,3-dipolar cycloaddition with azides. They react fast, and the yields of products are high. However, because the reacting... 

The intermolecular reaction of phenols with propiolic esters occurs in the presence of a Pd(OAc)2 catalyst to afford coumarin derivatives directly.48,48a An exclusive formation of 5,6,7-trimethoxy-4-phenylcoumarin is observed in the Pd(OAc)2-catalyzed reaction of 3,4,5-trimethoxyphenol with ethyl phenylpropiolate in TFA (Equation (46)). Coumarin derivatives are obtained in high yields in the cases of electron-rich phenols, such as 3,4-methylenedioxyphenol, 3-methoxyphenol, 2-naphthol, and 3,5-dimethylphenol. A similar direct route to coumarin derivatives is accomplished by the reaction of phenols with propiolic acids (Equation (47)).49 A similar reaction proceeds in formic acid at room temperature for the synthesis of coumarins.50,50a Interestingly, Pd(0), rather than Pd(n), is involved in this reaction. 

Propiolic acids. The ylide derived from 1 converts aldehydes into propiolic esters or the acids in 50-70% yield. 

Ethyl propiolate Propiolic acid, ethyl ester (8) 2-Propynoic acid, ethyl ester (9) (623-47-2)... 

An example of the second type of modification is the application of the Diels-Alder cycloaddition reaction to polders and copol ers containing pendant or backbone furan moieties. The use of bis-dienophiles such as propiolic acid and its esters or bis-maleimides provides a means of crosslinking based on multiple bridging by the double interchain lycloadditions. The thermal reversibility of these reactions allows the return to the original linear structure (thermoplastic material) by simply heating the gel. 

Generally, the isomeric l,2,4-triazoIo[4,3-a]pyrimidines (such as 18, Section II,B,1) are not formed. Exceptions are found with 3-phenyl-AT (60JOC361) and condensations of propiolic acids and their esters (70CB3266 71CB2702) [and, as minor side reactions, condensations of 3-ketovinylic compounds (83S44)]. 

Propiolic acid, 58,43 Propionaldehyde, 58, 80, 82 Propionic acid, 2-iodo-3-mtro-, ethyl ester, 56, 65... 

Enaminonitriles (154) easily react with esters of acetylenedicarboxylic acid or propiolic acid. The first step is an electrophilic attack of the reactant on the /3-position of the enamine, and this is followed by cyclization with... 

Trialkylphosphines add via anti addition to give the expected salts (577 Scheme 81) which decompose upon work-up to products (578) not containing phosphorus.145 Triethyl phosphite (equation 132) reacts with propiolic acid (572) or methyl propiolate (506) to give predominately (>90%) the P-phos-phono ester (579) with the ( -configuration.l4Sb... 

The cyclopropyl-allyl rearrangement has been shown to proceed with nucleophilic assistance,87i232<233 and the intermediate allyl cation can be trapped by nucleophiles leading to synthetically useful derivatives. An example is the formation of an unsaturated acetal and the propiolic acid ortho ester (equations 92 and 93).232... 

Treatment of aziridinyl ketone 18 with propiolic acid ethyl ester 58 leads to two regioisomeric pyrroles 59 and 60 [76] (Scheme 1.15). The reaction of ketone... 

It is necessary to prepare first, o-nitro-phenyl-propiolic acid, which is itself obtained from o-nitro-cinnamic acid. Cinnamic ester (50 gms.) is nitrated by pouring gradually into cooled nitric acid (sp. g. 1-5). 

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